Dipole antenna array having equally spaced dipoles of decreasing lengths



Dec. 2. 1969 w. s. MANER 3,482,250

DIPOLE ANTENNA ARRAY HAVING EQUALLY SPACED DIPOLES OF DECREASING LENGTHS3 Sheets-Sheet 1 Filed Oct. 6, 1966 4 FIG.

INVENTOR W/LL/AM s. M/u/ee ATTORNEY Dec. 2. 1969 W. S. DIPOLE ANTENNAARRAY HAVING EQUALLY SPACED DIPOLES 0F DECREASING LENGTHS Filed Oct. 6,1966 MANER 3 Sheets-Sheet 2 W/l 1 64M MJ/VEK ATTORNEY Dec.2,1969 s MAQER3,482,250

DIPOLE ANTENNA ARRAY HAVING EQUALLY SPACED DIPOLES OF DECREASING LENGTHSFiled Oct. 6, 1966 3 Sheets-Sheet (5 INVENTOR F/ 9 M4 1/4/11 5. AMA FeATTORNEY United States Patent O U.S. Cl. 343-766 Claims ABSTRACT OF THEDISCLOSURE This invention relates to the art of antennas, moreparticularly of the unidirectional type, to receive television signals,said antenna comprising a pair of elongated vertically aligned parallelbars with a plurality of pairs of receiving elements extending outwardlyfrom the sides of said bars and equally spaced along the length thereof.

As conducive to an understanding of the invention it is noted that as atelevision receiving point is progressively moved away from the signalsource, the power of such signal materially decreases.

To counteract this decrease in power, so-called high gain antennas havebeen employed, positioned at a relatively great height above the groundby the use of masts or the like.

When the receiving point is relatively close to the transmitter, say adistance of twenty-five miles, the use of an elevated antenna isgenerally satisfactory since the strength of the transmitted signal atsuch moderate distance is normally sufficient to suppress undesiredsignals. However, beyond the twenty-five mile range, for example, thepresent so-called high gain antennas do not operate satisfactorily. Thisis due to the unwarranted noise of undertermined and composite originwhich is picked up by the antennain an omni-directional manner. Whenthis noise is presented along with the desired signal to the televisionantena, the overall effect is to sharply degrade the quality of thepicture appearing on the television tube.

Further, when the receiving point is between two stations transmittingon the same frequency, if the antenna is not able to exclude theunwanted station, the resultant picture will be distorted.

Furthermore, since television antennas are generally inaccessible formaintenance, it is an important criteria in their design that they beable to withstand relatively high Wind velocities and inclement weather.

The design criteria of an eflicient television antenna would thereforehave to satisfy a number of problems. For example:

(a) The antenna must withstand wind velocities of fifty miles per hourunder an ice load of one-half inch;

(b) The material from which the antenna is fabricated must have aminimum life of approximately five years;

(c) The overall length of the antenna should not exceed twelve feet;

(d) The boom and elements of the antenna mounted thereon must havesufficient inherent strength so as to minimize bracing;

(e) The antenna design must be such as to facilitate manufacture,shipping and installation.

(f) The antenna should possess a flat frequency response over thefrequency range of 54 mc. to 216 mc. which cover the major existingtelevision channels;

(g) The antenna should have a uniform flat gain of or .5 db;

(h) The antenna should have a variable standing wave ratio of 1.2 to 1,as measured at the output terminals;

(i) The antenna should possess high front to back and front to sideratios of at least db down;

(j) The overall antenna gain should be a minimum of 12 db;

(k) The antenna should possess a very narrow front radiation lobe, thusyielding sharp directivity to the desired signal source.

The use of conventional antennas, such as the yagi type, the multipledipole and log periodic type, failed to solve the existing problem dueto the fact that none of these antennas possessed all of the desiredqualities.

It is, accordingly, among the objects of the invention to provide atelevision receiving antenna that may readily be fabricated by massproduction methods from relatively inexpensive materials that are strongand durable, which antenna may readily be shipped in disassembled formin a relatively compact container and which may readily be assembledwith simple tools, and when installed will be capable of withstandinghigh winds and inclement weather with a minimum of bracing, and whichwill be capable of receiving the desired signal, while at the same timerejecting unwanted noise and co-channel transmissions, thereby providinga picture of extreme clarity.

In view of the fact that the antenna per se is highly directional, it isimportant that such capability be utilized to the best advantage.

Where the antenna is mounted on a mast and a motor is employed to rotatethe antenna in steps, exact directional positioning of the antenna withrespect to a particular signal source is not possible.

Where the transmission line from the antenna is fed to an amplifierlocated adjacent the television receiver, due to the length of thetransmission line, stray signals could be picked up by the line ofstrength often greater than the relatively weak signals picked up by theantenna, with the result that the picture will be unsatisfactory.

It is accordingly another object of the invention to provide an antennasystem employing an antenna of the above type in which the antenna iscapable of being oriented so that it can be directly aimed as desiredtoward the signal source to be received and in which the signaltransmitted from the antenna to the television receiver is immediatelyelectronically amplified at the physical location of the antenna, thusyielding a signal strength far in excess of any undesired signal pickedup by the transmission line from the antenna to the television receiver.

According to the invention, these objects are accomplished by thearrangement and combination of elements hereinafter described and moreparticularly recited in the claims. a

In the accompanying drawings in which are shown one of various possibleembodiments of the several features of the invention,

FIG. 1 is a diagrammatic view of an antenna system according to theinvention.

FIG. 2 is a perspective view of the antenna.

FIG. 3 is a side elevational view of the antenna.

FIG. 4 is a top plan view of the antenna.

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4.

FIG. 6 is a detail view of an enlarged scale of the rear end of theantenna.

FIG. 7 is a view similar to FIG. 6 of the front end of the antenna.

FIG. 8 is a sectional view taken along line 88 of FIG. 3 showing themounting bracket, and

FIG. 9 is a schematic view of the antenna.

Referring now to the drawing, the antenna 10 comprises a pair of hollowelongated bars 11, 12, desirably of extruded aluminum, each preferablyrectangular in cross section and illustratively of one inch squarealuminum tubing having a wall thickness of inch.

The bars 11 and 12 are maintained in spaced parallel vertically alignedrelation by means of a plurality of insulating straps 13 spaced alongthe length thereof to define the antenna boom which mounts the receivingelements R.

In order to neutralize the effect of the boom on the receiving elementsR for optimum performance of the antenna, the boom length is selected tobe one wave length of a frequency that falls in the frequency spectrumabove the FM band (108 me.) and below the frequency of channel 7 (174mc.). The frequency selected is preferably 123 me. which is not one ofthe television transmitting frequencies so that in the preferredembodiment shown the boom length is 96 inches. As a result, standingwaves reflections and harmonics that could interefere with the receptionof the desired signals are eliminated.

The ends 14, 15 of the bars 11, 12 are connected by means of a U-shapedbracked 16 of conducting material, the legs 17 of which extend into theopen ends 14, 15 of the bars and are secured thereto as by screws 18,thereby shorting such bars. The short will occur exactly one wavelengthfrom the front of the boom defined by the ends 19, 20 of the bars. As aresult, the back of the antenna defined by the end 14, 15 of the bars,will be at zero potential which maintains the front to back ratio andalso maintains the side lobe suppression characteristics of the antenna.

A plurality of pairs of rods R, illustratively nine in number and ofvarying lengths and designated R1, Rl, R2, R9, R'9, which define thereceiving elements of the antenna, are secured to the bars 11 and 12along the length thereof and extend outwardly therefrom at right anglesthereto. Each of the rods R preferably is an extruded aluminum tube,desirably circular in cross section, and illustratively having adiameter of /2 inch and a wall thickness of .035 inch.

As shown in FIG. 2, the rods R of each pair are alternately secured tobars 11 and 12 and extend outwardly from one side thereof and the rods Rare alternatively secured to bars 12 and 11 and extend outwardly fromthe other side thereof. The rods of each pair extend in different plansand are transversely aligned.

Thus, the elements R of the antenna are staggered so that each half of apair of elements is 180 degrees out of phase with the other. The signalwhich strikes the elements in a perpendicular fashion will maintain a.correct phase relationship and will be additive at the feed point.Signals which arrive on the sides or at an angle to the front willinduce a phase shift between the corresponding elements. This in turnwill cause a cancellation at the feed point.

More particularly, to mount the rods R, each of the bars 11, 12, hastransversely aligned pairs of openings 21, 21', through which the end ofan associated rod R extends, being secured in position as by set screw22.

The pairs of rods R form dipoles, which are equally spaced along thelength of the bars with the longer rods R9 related to the lowestfrequency to be received (illustratively 54 me.) being adjacent the rearends 14, 15 of the bars and the shorter rods R1 related to the highestfrequency to be received (illustratively 216 me.) being adjacent thefront ends 19, 20 of the bars.

Each of the pairs of rods R at the front and rear of the boom is oflength substantially equal to one-half wavelength of the associatedfrequency, i.e., 54 me. and 216 me.

In determining the lengths of the intervening pairs of rods,experimentation clearly indicated that the rods should, first of all beequally spaced along the boom from front to back.

The length of the rods was determined by cutting them to a size equal tothe distance between an imaginary line connecting the ends of the firstand last element and a point perpendicular to the boom at the locationon the boom where the specific element was to be located.

Following the above described procedure, the proper number of elementswas determined by experimentation to yield maximum efficiency on all thedesired television channels.

To provide an output from the antenna, as shown in FIG. 7, a co-axialfitting 31 is mounted on the end 20 of bar 12. The outer shieldconductor 32 is electrically connected to bar 12 and the inner conductor33 extends through the bar 12 and is connected as at 34 to the end ofthe bar 11.

Thus, referring to FIG. 9, the outer conductor 32 will be connected torods R9, R8, R7, R6, R'S, R4, R3, R2, R'l, secured to bar 12 and theinner conductor 33 will be connected to rods R9, R'S, R7, R6, R5, R'4,R3, R'2, R1 secured to bar 11.

The antenna above described is thus designed on a linear concept basiswith the elements equally spaced along the length of the bar.

The antenna is preferably mounted on a vertical mast 36 which has amounting pad 37 at its upper end. Secured to said pad is a housing 38which contains a wide band amplifier 39 and a motor 41. The shaft 42 ofthe motor 41 is secured to the antenna by means of U-bolts 43 whichextend through a mounting plate 44 bolted to the bars 11, 12 to supportthe antenna at right angles to the shaft 42. A feed cable 45 isconnected at one end to fitting 31 on bar 12 and at its other end to theamplifier 39 and a transmission line 46 which illustratively carries apower cable for the motor, and an RF transmission line for the signal,extends down the mast 36 to a control box 47 which may be positioned ontop of the television receiver 48. The control box 47 has a junction 49whereby the signal input of the television receiver 48 may be connectedto the RF transmission line and the rheostat (not shown) controlled bythe dial 51 is provided to energize the motor 41 to turn the antenna tothe desired position.

Thus, if a particular station is to be received, the dial 51 is turnedto rotate the antenna so that its ends 19, 20 are aimed toward suchstation. The proper setting will be determined when the received pictureis of optimum clarity. By reason of the fact that the received signal isamplified closely adjacent the antenna, the strength of the signaltravelling down the transmission line will be much greater than anynoise or unwanted signals picked up by such line.

As the rear end 14, 15 of the antenna is shorted, signals impinging onthe antenna from the rear will have substantially no effect on thedesired signal received from the station desired toward which the frontof the antenna is aimed.

The antenna above described will have the physical strength and liferequired and since all of the components thereof are readily assembled,shipping of the disassembled parts is facilitated.

The antenna arrangement above described provides all of the electricalcharacteristics required for optimum performance of the televisionreceiver at relatively great distances from the transmission point ofthe desired signal.

As many changes could be made in the above equipment, and manyapparently widely different embodiments of this invention could be madewithout departing from the scope of the claims, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. A television antenna comprising a pair of elongated bars defining aboom, means maintaining said bars in spaced parallel, vertically alignedrelation, a plurality of pairs of receiving elements extending outward,respectively, from the sides of said bars at right angles thereto, saidpairs of receiving elements being equally spaced along the length of theboom, the elements on each side of said bars being alternately securedthereto, the length of the receiving elements at one end of the boombeing greater than the length of the receiving elements at the other endof the boom, the lengths of the receiving elements between the ends ofthe boom progressively decreasing from the longer elements to theshorter elements, means to short circuit the ends of the bars associatedwith the longer receiving elements and means to connect an output leadto the other ends of the bars.

2. The combination set forth in claim 1, in which said antenna isdesigned to receive signals in a given frequency range from a pluralityof transmission sources, each having a given transmission frequencyfalling in such range and said boom is of length related to onewavelength of a frequency within said range and distinct from any ofsaid transmission frequencies.

3. The combination set forth in claim 2 in which said frequency to whichthe length of the boom is related is approximately 123 me.

4. The combination set forth in claim 1, in which the pairs of elementsadjacent the ends of the boom are of length related, respectively, toone-half wavelenth of the lowest and highest frequencies to be receivedand each of the intervening pairs of elements, starting with the pairadjacent the pair related to the lowest frequency, is successively oflength equal to the distance from the boom to an imaginary lineconnecting the ends of the first and last elements.

5. The combination set forth in claim 1 in which each of said bars is analuminum tube and is rectangular in cross section and each of saidreceiving elements is an aluminum tube circular in cross section.

6. The combination set forth in claim 5 in which said bars have aplurality of pairs of vertically aligned openings spaced along thelength of the boom along each side thereof, each pair of openings on oneside being transversely aligned with a pair of openings on the otherside and one end of each of the elements of each pair of elements ispositioned in each of the transverse pairs of openings so that saidelements extend from opposed sides of said bars with one of the elementsof each pair being secured to one bar and the other to the other bar.

7. The combination set forth in claim 1, in which a conductive member issecured to the adjacent ends of said bars to short circuit said bars.

8. The combination set forth in claim 1, in which a plurality ofinsulating straps are provided, secured to said bars along the lengththereof to retain the bars in spaced parallel relation.

9. The combination set forth in claim 1, in which a mounting plate issecured to said bars, substantially midway between the ends thereof andin a plane perpendicular to the plane of said elements, an upright mastis provided, a motor and amplifier unit secured to the upper end of saidmast, said motor having a shaft, means securing said shaft to saidmounting plate, a transmission cable having a power lead connected tosaid motor and a radio frequency lead connected at one end to the outputof said amplifier, and a lead connecting the input of said amplifiertothe connecting means at the other ends of said bars.

10. The combination set forth in claim 9 in which means are provided toconnect said radio frequency lead to said television receiver.

References Cited UNITED STATES PATENTS 3,221,332 11/1965 Krauis et al343-792.5 3,259,904 7/1966 Blonder et al 343792.5

ELI LIEBERMAN, Primary Examiner US. Cl. X.R.

